1. Field of the Invention
The present invention relates to a transfer apparatus, in particular, to a transfer apparatus which is capable of carrying a thin, plate-like work such as a substrate, along a straight path.
2. Description of the Related Art
A transfer apparatus for carrying a thin platy work is disclosed in JP-A-2005-186259, for example. The conventional transfer apparatus includes a swivel and a pair of link arm mechanisms (linear movement mechanisms) provided thereon. Each of the link arm mechanisms has its end portion provided with a hand which is capable of holding a platy work such as a substrate horizontally. The swivel is supported by a cylindrical lift base (lift member) which can be raised and lowered relative to a fixed base. The lift base is raised or lowered in order to move the hand which is supported by the swivel to a predetermined height. As the swivel turns on the fixed base, about a vertical axis, the pair of link arm mechanisms rotate therewith, and as the link arm mechanisms swing to open, the platy works held by the hands are moved linearly on a horizontal plane, transporting the platy works from a predetermined location to another location.
The transfer apparatus which includes such a linear movement mechanism as the above is used in manufacturing processes of semiconductor devices or liquid crystal display panels for example, in order to move a work in and out of process chambers. When carrying a work in and out of different process chambers, the carrying process can be achieved by a chain of transportation operations for example, via a vacuum transportation module which is disposed between an atmospheric transport module and each process chamber. The vacuum transport module includes a transport chamber surrounded by a plurality of process chambers, and a load lock which connects the atmospheric transport module with the transport chamber. In the transport chamber, there is disposed a transfer apparatus which is of the type described above and is capable of operating in a vacuum environment. The transfer apparatus receives a work in the load lock, transports the work into the transport chamber, and then into one of the process chambers while receiving a processed work from the process chamber and moving it to the load lock. In the load lock, there is a stage for placing a work, and the work is delivered to and picked from this stage.
In recent years, the stage in the load lock sometimes has three or more tiers for a purpose of improved efficiency, for example, in the manufacturing process. When the transfer apparatus is used in a load lock equipped with such a multi-tiered stage, the lift base must have an increased lift stroke. However, increasing the stroke generally leads to a consequence that the lift base's vertical (height direction) dimension is increased, as well as the height dimension of the fixed base which supports the lift base. This leads to an undesirable trend of overall increase in the size of the transfer apparatus.